Dry etching apparatus

ABSTRACT

An etching chamber has a lower electrode section and an upper electrode section. A semiconductor wafer WF is mounted on the lower electrode section. An outer ring including a silicon (Si) ring disposed around the lower electrode section to provide a positioning assistance in mounting the semiconductor wafer WF, and an aluminum (Al) ring disposed under the Si ring. The Si ring virtually expands the area of a wafer WF when plasma is generated, such that unstable plasma around the wafer can be stabilized. To reduce localized abrasion and further stabilize plasma, the Si ring has a height-changing portion. The height-changing portion is formed of a curved surface in the innermost part and function to position the wafer WF.

[0001] Japanese Patent Application No. 2001-387, filed on Jan. 5, 2001, is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a semiconductor manufacturing apparatus, more particularly to a dry etching apparatus in which etching gas is introduced into an etching chamber and plasmatized therein to etch a semiconductor wafer.

[0003] A dry etching apparatus is an apparatus used in a process of manufacturing semiconductor devices, supplies required etching gas to wafers and selectively etches the wafers. A recently and commonly used technique is a technique using plasma etching in which etching gas introduced into an etching chamber is plasmatized.

[0004]FIG. 4 schematically shows a structure of main components of a conventional dry etching apparatus. An etching chamber 40 includes a lower electrode section 41 and an upper electrode section 42. A semiconductor wafer WF is mounted on the lower electrode section 41. A gas introduction pipe 44 is connected to a mass-flow control valve or the like (not shown) through which various gases at predetermined amounts are flown from gas units to supply etching gas EG to the chamber 40. Discharge of a high frequency power supply RF is excited by the upper electrode section 42 and the lower electrode section 41 such that plasma is generated.

[0005] An outer ring 43 that provides a positioning assistance in mounting the semiconductor wafer WF is provided around the lower electrode section 41, and the outer ring 43 is formed of a silicon (Si) ring 431 of the same material as the wafer and an aluminum (Al) ring 432 that is provided under the Si ring 431 to support the Si ring 431. The Al ring 432 is supported by other components (not shown). The Si ring 431 has a step 431 s for positioning the wafer WF on the innermost side, and the step 431 s has a sloped part of a predetermined angle. The Si ring 431 virtually expands the area of the wafer WF when plasma is generated such that unstable plasma along the outer part of the wafer can be stabilized.

[0006] In the structure described above, the etching gas EG introduced into the etching chamber 40 is plasmatized into plasma etching gas by glow discharge excited between the upper electrode section 42 and the lower electrode section 41 by high frequency (RF) power from the high frequency power supply RF. The plasma etching gas achieves a plasma etching treatment on the semiconductor wafer WF. After reaction, an exhaust pipe 45 mainly conducts exhaust gases outside the etching chamber 40.

[0007]FIG. 5 shows an enlarged view of the Si ring of FIG. 4. In etching, plasma concentrates in a section 51 of the Si ring 431. In other words, plasma strikes and rebounds on the sloped part or corners of the step 431 s in the Si ring 431, or on a side (end surface) of the wafer WF, and concentrates in a local portion in which an excessive abrasion occurs.

[0008] If localized abrasion and deterioration of the Si ring 431 as in the section 51 in FIG. 5 advance, the plasma stability around the wafer WF cannot be maintained, and the etching rate in a region around the wafer WF is lowered. Therefore, if the Si ring 431 in which localized abrasion and deterioration have advanced to a certain degree is used, the etching uniformity and etching rate are kept at the lowest level of standard. Consequently, the quality tends to deteriorate, leading to defective etching.

[0009] To avoid the quality deterioration, the Si ring 431 needs to be replaced early. In other words, the service life of the Si ring 431 unavoidably becomes shorter because the Si ring 431 has large localized abrasion and deterioration due to it.

[0010] Also, as the chamber is used for a longer time, deposits 52 that have not been eliminated may accumulate in a gap between the lower electrode 41 and the Si ring 431 and the Al ring 432 to the extent that the gap is filled with the deposits. If localized abrasion in the Si ring 431 is advanced, the accumulation of the above-described deposits 52 is substantially increased, and the gap tends to be stuffed earlier. This makes it difficult to remove the Si ring 431 at the time of cleaning the chamber. Also, the Si ring 431 could strongly adhere to the Al ring 432. Consequently, problems arise in that the Si ring is damaged when it is removed, the cleaning time increases, and so forth.

BRIEF SUMMARY OF THE INVENTION

[0011] The present invention has been made in view of the problems described above, and it is an objective of the present invention to provide a dry etching apparatus having a structure in which plasma stability can be maintained, and the service life of an outer ring such as a silicon (Si) ring in a chamber can be extended.

[0012] According to one aspect of the present invention, there is provided a dry etching apparatus having a chamber and plasmatizing an etching gas introduced into the chamber to conduct a required etching, the dry etching apparatus comprising:

[0013] a first electrode section provided in the chamber and having a support section for a semiconductor wafer;

[0014] a second electrode section provided in the chamber to face the first electrode section; and

[0015] an outer ring for mounting the semiconductor wafer, which is disposed around the first electrode section,

[0016] wherein the outer ring includes a height-changing portion formed of at least a curved surface on the innermost side.

[0017] In the above dry etching apparatus, instead of the angled step, a height-changing portion composed of a curved surface is provided on the innermost part of the outer ring. As a result, localized concentration of plasma can be almost avoided.

[0018] In this dry etching apparatus, the curved surface may be concave.

[0019] According to another aspect of the present invention, there is provided a dry etching apparatus having a chamber and plasmatizing an etching gas introduced into the chamber to conduct a required etching, the dry etching apparatus comprising:

[0020] a first electrode section provided in the chamber and having a support section for a semiconductor wafer;

[0021] a second electrode section provided in the chamber to face the first electrode section;

[0022] a first outer ring for mounting the semiconductor wafer which is disposed around the first electrode section; and

[0023] a second outer ring that is disposed below the first outer ring and has an internal diameter larger than the internal diameter of the first outer ring such that a distance from the second outer ring to the first electrode section is larger than the distance between the first outer ring and the first electrode section,

[0024] wherein the first outer ring includes on the innermost side a height-changing portion formed of at least a curved surface.

[0025] In the above dry etching apparatus, instead of the angled step, a height-changing portion composed of a curved surface is provided on the innermost part of the first outer ring. As a result, localized concentration of plasma can be almost avoided. Furthermore, the second outer ring having an internal diameter larger than that of the first outer ring is provided below the first outer ring, such that a sufficiently large distance is provided between the first electrode and the second outer ring. This makes it difficult for deposits to accumulate in a gap between the first and second outer rings and the first electrode section.

[0026] In this dry etching apparatus, the curved surface may be concave.

[0027] In this dry etching apparatus, the first outer ring may be changeable independent of the second outer ring.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0028]FIG. 1 schematically shows a structure of main components of a dry etching apparatus in accordance with a first embodiment of the present invention.

[0029]FIG. 2 shows an enlarged view of the Si ring in FIG. 1.

[0030]FIG. 3 schematically shows a structure of main components of a dry etching apparatus in accordance with a second embodiment of the present invention.

[0031]FIG. 4 schematically shows a structure of main components of a conventional dry etching apparatus.

[0032]FIG. 5 shows an enlarged view of the Si ring in FIG. 4.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033]FIG. 1 schematically shows a structure of main components of a dry etching apparatus in accordance with a first embodiment of the present invention. Here, a narrow-gap parallel plate type apparatus is explained as an example. An etching chamber 10 includes a lower electrode section 11 and an upper electrode section 12. A semiconductor wafer WF is mounted on the lower electrode section 11. A gas introduction pipe 14 is connected to a mass-flow control valve or the like (not shown) through which various gases at predetermined amounts are flown from a gas unit to supply etching gas EG to the chamber 10. Discharge of a high frequency power source RF is excited by the upper electrode section 12 and the lower electrode section 11 such that plasma is generated.

[0034] The lower electrode section 11 is processed by an insulation film coating (or Alumite coating) except a region in which the wafer WF is disposed. An outer ring 13 for mounting the semiconductor wafer WF is provided around the lower electrode section 11, and the outer ring 13 is formed of a silicon (Si) ring 131 of the same material as the wafer and an aluminum (Al) ring 132 that is provided under the Si ring 131 to support the Si ring 131. The Al ring 132 is supported by other components (not shown). The Si ring 131 functions to virtually expand the area of the wafer WF when plasma is generated, such that unstable plasma around the wafer can be stabilized.

[0035] In this embodiment, the Si ring 131 has a height-changing portion 131 h on the innermost side, and the height-changing portion 131 h has a curved surface and is used to position the wafer WF.

[0036] In the structure described above, the etching gas EG introduced in the etching chamber 10 is plasmatized (into plasma etching gas) by glow discharge excited between the upper electrode section 12 and the lower electrode section 11 by high frequency (RF) power from the high frequency power supply RF. The plasma etching gas achieves a plasma etching treatment on the semiconductor wafer WF. After reaction, an exhaust pipe 15 mainly conducts exhaust gases outside the etching chamber 10.

[0037]FIG. 2 shows an enlarged view of the Si ring in FIG. 1. The height-changing portion 131 h of the Si ring 11 is composed of a curved surface as described above. This can almost prevent localized abrasion and deterioration caused by plasma concentration in etching. In other words, unlike the conventional technique, it is difficult for plasma to reflect at fixed angles and to concentrate locally. This makes it easier to maintain plasma stability around the wafer WF, such that the etching rate around the wafer WF is not seriously lowered. Accordingly, the service life of the Si ring 131 is extended, and the quality is improved since the etching uniformity is maintained.

[0038] In accordance with the embodiment described above, localized abrasion and deterioration in the Si ring 131 can be almost prevented, and therefore the service life of the Si ring 131 can be extended. Also, deposits between the lower electrode 11 and the Si ring 131 and the Al ring 132 are reduced. As a result, this makes it easy to remove the Si ring 131 and the Al ring 132 when the chamber is cleaned. Since the time required for cleaning can be shortened, the efficiency of etching process can be improved.

[0039]FIG. 3 schematically shows a structure of main components of a dry etching apparatus in accordance with a second embodiment of the present invention. In this dry etching apparatus, an Al ring 132 for supporting the Si ring 131 has a different structure from that of the first embodiment. As shown in the figure, the Al ring 132 has an internal diameter greater than that of the Si ring 131 such that a distance d2 between the Al ring 132 and the lower electrode section 11 becomes larger than a distance d1 between the Si ring 131 and the lower electrode section 11. Since other components are the same as those of the first embodiment, they are denoted by the same reference numbers and further description is omitted.

[0040] With the structure of the Al ring 132 described above, the distance d2 from the lower electrode section 11 becomes sufficiently large. If the distance d1 between the lower electrode section 11 and the Si ring 131 is 1 mm or less, and the distance d2 between the lower electrode section 11 and the Al ring 132 may be set at about 5 mm. By providing a sufficient distance (d2) between the lower electrode section 11 and the Al ring 132 that is thicker than the Si ring 131, deposits are difficult to accumulate in a space between the ring and the lower electrode section 11. As a result, deposits that gradually accumulate while the etching chamber is used for a long time tend to drop to a bottom section 11 b of the lower electrode section 11 rather than stick to an upper portion of the lower electrode section 11 adjacent to the Si ring 131.

[0041] In accordance with the embodiment described above, localized abrasion and deterioration in the Si ring 131 can be almost prevented by the structure of the height-changing portion 131 h. In addition, deposits that may adhere in a space between the lower electrode 11 and the Si ring 131 and the Al ring 132 can be substantially reduced by the structure of the Al ring 132 that provides a sufficient distance d2 between the Al ring 132 and the lower electrode section 11. As a result, the service life of the Si ring 131 can be extended. Also, the Si ring 131 and the Al ring 132 can be readily removed when the chamber is cleaned, and the cleaning time can be shortened, with the result that the efficiency of etching process can be improved.

[0042] It is noted that, in the embodiments described above, the outer ring 13 includes the Si ring 131 and the Al ring 132, but it is not limited thereto. Any supporting ring instead of the Al ring 132 may be used, or it may have a structure that is composed only of the Si ring 131. In any of the cases, an innermost part of an outer ring (the Si ring 131) that is exposed to plasma and also serves for positioning, is formed of a curved surface to reduce the plasma concentration. Accordingly, deposits can be reduced by reducing localized deformation in an outer ring (the Si ring 131) and maintaining plasma stability around a wafer.

[0043] As described above, in accordance with the present invention, an angled step on the innermost side of an outer ring is replaced by a height-changing portion formed of a curved surface to almost reduce the plasma concentration and to stabilize plasma. Furthermore, when a second outer ring is provided under the outer ring that is exposed to plasma, an internal diameter of the second outer ring can be made larger to make it difficult to accumulate deposits in a gap between the second outer ring and the first electrode section. As a result, there is provided a dry etching apparatus having a structure in which plasma stability can be maintained and the service life of an outer ring such as a silicon ring within a chamber can be extended. 

What is claimed is:
 1. A dry etching apparatus having a chamber and plasmatizing an etching gas introduced into the chamber, the dry etching apparatus comprising: a first electrode section provided in the chamber and having a support section for a semiconductor wafer; a second electrode section provided in the chamber to face the first electrode section; and an outer ring for mounting the semiconductor wafer, which is disposed around the first electrode section, wherein the outer ring includes a height-changing portion formed of at least a curved surface on the innermost side.
 2. The dry etching apparatus as defined in claim 1, wherein the curved surface is concave.
 3. A dry etching apparatus having a chamber and plasmatizing an etching gas introduced into the chamber, the dry etching apparatus comprising: a first electrode section provided in the chamber and having a support section for a semiconductor wafer; a second electrode section provided in the chamber to face the first electrode section; a first outer ring for mounting the semiconductor wafer which is disposed around the first electrode section; and a second outer ring that is disposed below the first outer ring and has an internal diameter larger than the internal diameter of the first outer ring such that a distance from the second outer ring to the first electrode section is larger than the distance between the first outer ring and the first electrode section, wherein the first outer ring includes on the innermost side a height-changing portion formed of at least a curved surface.
 4. The dry etching apparatus as defined in claim 3, wherein the curved surface is concave.
 5. The dry etching apparatus as defined in claim 3 and 4, wherein the first outer ring is changeable independent of the second outer ring. 